This invention relates to storage systems, and in particular a method and apparatus for preparing storage systems for initial use.
Modern storage systems are capable of storing thousands of gigabytes of data using large numbers of hard disk drives or other storage media. When the system is first used, however, it is necessary that the system be physically initialized by having each of the hard disk drives or other media suitably prepared for use. This operation is often referred to as “formatting” the storage media. Initializing or formatting positions various markers on the hard disk drives to designate where information is to be stored. It usually also is used to write desired “null” data onto the disk to assure that all of the bits are in a defined state. The null data may consist of a pattern of 0's, or 1's, or some mixture of the two. Sometimes this initialization process is also done after the system has been in operation for a period of time, for example to reset the system or to remove information from the disks that is no longer wanted, etc. Initializing large storage systems can require many hours, precluding their use by the user or the system within which they are installed, until all of the hard disk drives are initialized. This is undesirable.
Some initialization techniques do not rewrite all of the data regions on the disk, instead clearing only the directory information—in effect removing data from the disk by removing an entry in the index to allow that location to be later reused. Such procedures have become known as “quick” initialization or formatting. These procedures require that the disk have been initialized at some prior time. In addition, quick initialization has a disadvantage of leaving data on the disk. Thus, a “read operation” to a portion of the disk in which only the directory was initialized, may result in the return of incorrect data.
U.S. Pat. No. 6,467,023 describes a method for creating logical units in a RAID storage system and making those units immediately available. Although its purpose is similar to that described herein, it does not describe operations for unformatted areas of the disk. It also does not teach initializing as a background operation. A background copy may be implemented using details of the “Flash Copy” capability described in the IBM RedBook “Implementing ESS Copy Services on S/390” at section 4.8.